Spinner Shark

With a recent email I received about a spinner shark caught on tape I thought this would be the perfect time to blog about it.

Scientific name: Carcharhinus brevipinna

Common name: Spinner shark, Longnose grey shark, Inkytail shark, and Smoothfang shark

Identification: The snout is laterally pointed and has well developed labial furrows (shallow grooves around the lips). Eyes are small and round. Interdorsal ridge is absent. Dorsum grey with indistinct white line on flank. Ventrum is white. Distinct and boldly delineated black tips on all fins except pelvic and upper caudal. Anal fin is more "hooked" than in most large reef sharks. Angular torso with well defined lateral line. Teeth are narrow cusped.

Size: Maximum length is 278 cm. With birth size ranging from 60-75 cm.

Habitat: Continental coastlines from inshore to edge of shelf. Surface water to bottom at 75 m.

Distribution: Western Atlantic from Carolinas to Gulf of Mexico. Southern Brazil. Occasional Craibeean and northern Brazil. Eastern Atlantic around western Africa and Southern Mediterranean Sea. Around perimeter of Indian Ocean from Madagascar to South Africa. Also India, Southeast Asia and Australia. North Pacific Japan and Philippines.

Behavior: Some subspecies of the spinner shark are migrational. Some species will live in enormous schools of females with the males only joining during mating season. When feeding, vertical upward attacks on surface fish lead to spectacular spinning jumps from the water.

Diet: consists mainly of bony fishes, but can include stingrays and cephalopods.

Reproduction: Viviparous with a yolk sac placenta. Litter size can range from 3-20 based on the size of the female shark.

Reaction to humans: VERY SHY! It is commonly seen by fishermen when breaching, but it will quickly move away when a human enters the water. Unlike other sharks even when there is chum in the water it will keep its distance.

IUCN Red List Status: Near threatened. Vulnerable to fishing pressure and habitat degradation.



The spinner shark is a species of requiem shark,* family Carcharhinidea. It's name comes from the spinning leaps it makes as a part of its feeding strategy, hence the name. The spinner shark can be found in tropical to warm waters worldwide, except for in the eastern Pacific Ocean. It is usually found from coastal to offshore habitats to a depths up to 100m, even though it prefers shallower waters. The spinner shark is sometimes mistaken for a blacktip shark because of its slender body, long snout, and black-marked fins. This species can be distinguished from the blacktip shark by the first dorsal fin, which has a different shape and is placed further back, and by the black tip on the anal fin (adults only).

Spinner sharks are swift and gregarious predators that fed on a wide range of small bony fishes and cephalopods. These sharks are minimal to no threats to humans as their teeth are created to crush small fish. When feeding on schools of fish, they will speed vertically through the school while spinning on their axis, erupting from the water at the end. Which is what you can see in this attached link's video.

Like other members of the Carcharhinidae family, spinner sharks are viviparous with a yolk sac placenta in their reproduction method. The females will usually bear litters of 3-20 young every other year. The pups are born in shallow nursery areas near the coast and are relatively fast-growing.

Spinner sharks play a large role in commercial fisheries. The meat is considered to be high quality and is either sold fresh or dried and salted. In the USA the meat is marketed under the name "blacktip shark" due to that species being considered even higher in quality by consumers. In addition, the fins are used for shark fin soup, while the liver oil is processed for vitamins, and the skin is made into leather products.

The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened worldwide and Vulnerable off the southeastern United States. The spinner sharks's frequent use of coastal habitats render it vulnerable to human exploitation and habitat degradation.

* Requiem sharks are a family, Carcharhinidea, of sharks in the order Carcharhiniformes, containing migratory, live-bearing sharks of warm seas (sometimes brackish or fresh water) such as the tiger shark, the blue shark, the bull shark, and the milk shark. Family members have the usual carcharhiniform characteristics. The eyes are round, and the pectoral fins are completely behind the five gill slits.

Happy World Ocean Day!

WOW!  Happy World Ocean Day totally creeped up on me this year.  Do you know what that means?  It means I live too far away from an ocean.  However, regardless of where you live, we all can do our part in protecting our oceans.

You might be thinking..."I don't live by an ocean so how can I do my part?"

Simply by being aware of the fish/seafood/sushi you buy....

Not all seafood is equal and consumers choice DO make a difference for ocean life. Today, many fishing practices worldwide are damaging our oceans, depleting fish populations, destroying habitats, and polluting the water.  With many populations of fish currently in a state of stress it is our job as consumers to insure that what we are buying is environmentally friendly seafood.

How do you do this?

The answer is....easily!

First, make sure the seafood you are about to purchase is from a healthy population and harvested in a sustainable non-destructive manner.  In the case of farmed/fatten fish (aquaculture, mariculture) the seafood should not be fed with endangered wild fish and the farm should not be an ecological hazard (e.g. pollution, risk of escaping fish) to the surrounding environment.  Secondly, buy locally caught or raised seafood rather than imported; this helps reduce the carbon footprint by cutting down on transportation fuel.  

There is a handful of Non-Governmental Organization (NGOs) that provide lists on fish to eat and to avoid.  Aimed at consumers these lists are very basic and simple to use.  They are usually in some form of a color code - with green being good and red being AVOID!  Many of these NGOs provide a wallet size print out for FREE!  This way you can always carry the card with you and refer to it before you buy.

But, where can I get one of these most awesome free seafood friendly pocket guides?

Have no fear!  For I am here!

Just click on this link: http://www.montereybayaquarium.org/cr/cr_seafoodwatch/download.aspx
and then print out the region that pertains to your location.  It is suggested that if you live by a border of two regions to print out both regions.

But, I don't want to always carry around a piece a paper....

I have an solution for this too...man, am I good or what?

Seafood Watch now provides an application for the iPhone and Android.

Just click here to learn about downloading the application: http://www.montereybayaquarium.org/cr/SeafoodWatch/web/sfw_iPhone.aspx

Now you have no excuse as to why you can't buy environmentally friendly fish, seafood, or sushi!  Happy eating!

P.S. - One more suggestion for celebrating Happy World Earth Day.  If you have a child, or children, or are a child at heart most local zoos celebrate Happy World Earth Day with fun activities.

Check out this link to found local celebrations in your area (includes activities worldwide): http://worldoceansday.org/?page_id=122

Enjoy celebrating!

Galveston (Surfside) Shark Attack

On Memorial Day 2011 a University of Houston senior, Kori Roberston, was bitten by a shark in the Surfside beach of Galveston, Texas.  However, this blog is not to give sharks a bad rap (for we all know they have a bad enough rap as it is), but it is to focus on the rarity of shark attacks and how you can help prevent, your already low chances, of becoming a victim.

When my friend, Jacquie Stauffer, forwarded me this story it hit home for me.  Not because I knew the young girl or because I am a fellow shark victim, but because I called these waters my personal "pool" for five years.  Just to reiterate the rarity of shark attacks, the whole time I lived in the Galveston area not once did I hear about a shark attack.  

Since this blog was prompted by a shark attack in Galveston, I would like to briefly look at the statics of previous shark attacks in Galveston and the surrounding counties (Nueces, Cameron, Matagorda, Brazoria, and Kleberg).  

Pulling data from, http://www.flmnh.ufl.edu/fish/sharks/statistics/GAttack/mapTexas.htm, we can analyze the number of shark attack in these counties from 1911-2010.  In Galveston county there have been a total of 14 shark attacks, with one fatal attack in 1911.  The second most shark attacks occurred in the Nueces county with 10, 0 fatal.  Cameron county has had 6 shark attack, one fatal attack in 1962.  Matagorda county had 2 attacks, while Kleberg and Kenedy have both had one shark attack, no fatal attacks in these counties.  Not only are shark attacks rare, but they are seldom fatal, with the last fatality from a shark attack being back in 1962 - 49 years ago!

When we take a look at what counties have a high area of shark attacks (Galveston and Nueces) we notice that both of these counties are located near a bay-area.  Many species of sharks utilize bays as breeding grounds (swallow, warm waters, abundant food supply, and protection for the pups to hide).  So could there be a correlation between counties located next to a bay area and a high number of shark attacks?

Sharks do not just attack people, we are not on their dinner menu, and in all reality they would personally like to avoid us for the most part.  However, a shark will attack if, 1) they accidentally mistake us for a snack, and 2) if we invade their territory.  There are additional steps you can take to reduce, your already low chances, of being the next victim of a shark attack.

1) Always swim in a group.
2) Don't wander too far from shore.
3) Avoid the water at night, dawn, or dusk for this is when sharks are most active.
4) Don't enter the water if bleeding.  Shark can smell and taste blood - tracing it back to the source.
5) Don't wear shiny jewelry.  The reflected light looks like shining fish scales.
6) Don't go into waters containing sewage.  Sewage attracts bait fish - bait fishes attract sharks.
7) Avoid water being fished and those with lots of bait fish.  If you see a lot of diving seabirds that is a good sign that there are bait fish in the water.
8) Don't enter the waters if sharks are present. Does this really need to be stated?
9) Avoid an uneven tan and brightly colored clothing. Sharks can see contrast extremely well!
10) Don't splash a lot.
11) Use care near sandbars or steep drop-offs - a shark's favorite hangout.
12) Don't try to touch a shark if you see one.  You are NOT the shark whisperer!
13)  If you have followed rules 1-12, but still find yourself being attacked by a shark, then "Do whatever it takes to get away!"  Some people have successfully escaped an attack by being aggressive, other passive, some yelled, and others blew bubbles, regardless of your action of choice, DO ANYTHING!  Personally, I would go down fighting - all is fair in love and war.    

References: 

http://www.flmnh.ufl.edu/fish/sharks/statistics/GAttack/mapTexas.htm

http://www.flmnh.ufl.edu/fish/kids/avoid.htm

Shark Reproduction

There hasn't been much research conducted in regards to shark reproduction, given the difficultly to obtain such data, but a great deal is known about the process.  For example,  we know that sharks are K-selected species, meaning, that they produce a small number of well-developed young, usually have a small clutch size, and are slow to mature.  We also know that shark conception generally takes place privately in the waters of the ocean and will seldom breed in captivity.

Male sharks have developed a special reproduction part - claspers.  Many people mistake the claspers for penises, thus the saying "Sharks have two penises!" Man, would female sharks be lucky if that saying was true.  The claspers are used to get the male sperm inside the female.

During shark "foreplay" the females will emit various types of chemicals into the water to attract the males.  This is because most species of sharks the males and females do not co-habitate the same area.  When a male shark is interested in mating with a female he will bite her to let her know...oh, KINKY!  No worries, the females are not hurt by this "love" bites, in fact, they have developed extra thick skin to protect them.  Some researchers believe this biting behavior also takes place during conception in order to help keep the two sharked entwined for the process to be completed.

Now, that we know all about a shark's foreplay, what about the birthing process?  Sharks are truly magically animals!  Not only have they been around for 409 million years, but they have evolved multiply reproduction/birthing methods.  There are three sexual methods in which a female can reproduce and one asexual way.

First, we will examine the sexual ways:

1)Viviparity: giving birth to live sharks
There are species of sharks, such as the blue shark, that give birth to live baby sharks, as known as pups. They only have a few at a time and they abandon them directly after birth.  From the moment the pups are born they instinctively know how to survive on their own.

2)  Oviparity: laying eggs
Other species of sharks, like the bull shark, will lay eggs in a well hidden area.  The eggs are incased in a  protective case that makes it difficult for predators to break into.  With this method of reproducing the clutch size can range from a few eggs to over 100 eggs

3) Ovoviviparity: eggs develop inside the mother
Most sharks, like the tiger shark, use this method of reproduction.  The eggs hatch inside the mother and they continue to be nourished by the yolk of the egg and some fluids from the mother.  Some species of shark's pups practice a form of cannibalism known as oophagy, which means they will eat the remaining eggs that have not hatched.

4) Asexual Reproduction: reproduction without a male
Sharks have evolved to be such specialized creatures that they not only reproduce sexually, but they can also reproduce asexually, when the environment is not conducive to sexual reproduction.  WOW!  There have been reported cases where female sharks in captivity have had no contact with a male, but become pregnant anyway.  This type of asexual reproduction is known as, parthenogenesis.  We know that parthenogenesis is possible among the female hammerheads.  This type of reproduction is extremely rare and in most cases does not occur.  However, this could be a significant reason as to why sharks have been able to survive for so many years with high population numbers.  It is speculated, however, that asexual reproduction does not take place too often in the wild, because of the abundance of males and the correct mating environment.  

References:

http://biology.about.com/b/2007/05/24/asexual-reproduction-in-sharks.htmhttp://www.marinebiodiversity.ca/shark/english/reproduction.htm

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California Shark Finning Ban Update

The San Francisco Chronicle is reporting that the California Assembly “overwhelmingly approved” (62-8 vote) a measure that could ban the sale and distribution of shark fins in the state. The bill (AB376) will now move on to the state Senate. If the bill is approved by the Senate, the shark fin ban will take effect on January 1, 2013.

The bill has been somewhat controversial since the ban of shark fins would result in making shark fin soup illegal. The soup is regarded as a Chinese delicacy. Opponents of the bill have claimed that the bill targets Asian cultures unfairly.

Shark Finning Advertising in San Francisco

In February of this year, I was in San Francisco visiting an old friend from high school.  Since, she had just given birth 2 weeks prior to my visit, plus she had a 2.5 year old, and myself a 6 month old, needless, to say we didn't get out of the house much.  However, one of the days, it was just too beautiful outside to pass up a trip to the beach.  Since we all couldn't fit in her car, we hopped on the San Francisco MUNI bus.  At first it was a shock, then a double turn, and then with great surprise that I would find an advertisement for shark finning on a bus in San Francisco.  However, seeing this ad filled my heart with warmth.  It was great to see some pro-active ads to stop shark finning right here in the good ol' USA.  


After I returned from the USA, I did a quick Google about the ads to gain more information about them.  This is what I discovered.   


Shark Savers has joined WildAid, Oceana, and the Humane Society in an advertising campaign to run in San Francisco MUNI buses to combat the consumption of shark fin soup. In addition to reducing shark fin soup consumption, the purpose of the campaign is to boost community awareness in the San Francisco Bay Area and support the ongoing efforts to pass the California Shark Fin Ban, AB376.

The campaign is running between March 21 and June 18, 2011, in both English and Chinese. It will run on over 275 queen, tail and interior ads will run on San Francisco MUNI buses.  Buses routes were chosen that run directly through Chinatown as well as other neighborhoods with high concentration of Asians such as Richmond, Excelsior and Sunset.

Three ads are running, now. Click on the image below to view some of the ads making their way through San Francisco.

Ad #1 is with NBA All-Star Yao Ming, asking consumers to Just Say No to shark fin soup. Click on the images below to expand the view.

Ad #2 talks about the high levels of of the neurotoxin mercury that is found in sharks at elevated levels.

Ad #3 addresses the act of shark finning and how up to 73 million sharks end up in shark find soup.

Source: http://www.sharksavers.org/en/blogs/729-sanfranciscoadcampaigncombatssharkfinsoup.html

The Horror of Shark Finning

If every picture is worth a 1,000 words, then this picture is worth a million words.  This shark is just one of million of sharks that fall victim to shark finning.  What is shark finning?  Shark finning refers to the removal and retention of shark fins with the rest of the shark being discarded back into the ocean.  The removal of a shark's fins occurs when the shark is still ALIVE.  However, the the torture for the shark is not yet over.  After the fins are removed the shark is thrown back into the water, still alive, to die a slow a painful death of suffocation on the bottom of the ocean.  You don't have to be a shark lover to see the inhuman acts shark finning thrushes upon these magnificent animals.  Shark finning is occurring all over the world and has increased over the past decade largely due to the increasing demand for shark fins for Chinese shark fin soup, traditional cures, improved market economics, and improved fishing technology (making it easier to find and catch sharks).       

Some researchers believe that from 1996 to 2000, 26 to 73 million sharks were traded yearly.  The annual median for the period was 38 million nearly four times more than the UN estimates, but considerably lower than those of many conservationists.

Shark finning is a billion dollar industry that needs to be STOPPED!  Sharks can not endure this kind of fishing pressure much longer.

For further information on shark finning, please read my following paper (you will have to copy and paste the link).

file:///Volumes/PUBLIC/School%20Related%20Folders/Shark%20Papers%20and%20Sources/Shark%20Finning.htm